Arc resistant drive with bypass and synch transfer

ABSTRACT

The systems and methods disclosed relate to arc resistant medium voltage motor control centers for bypass and synch transfer. A drive control system comprising: a variable frequency drive cabinet comprising a variable frequency drive; a power supply line; at least one motor control cabinet having a top portion and a bottom portion, wherein the at least one motor control cabinet is arc resistant, wherein the at least one motor control cabinet comprises: a medium voltage fused bypass controller in the top portion; a medium voltage non-fused transfer controller in the bottom portion; a reactor compartment, wherein the reactor compartment is arc resistant; wherein the variable frequency drive is coupled to the power supply line and the non-fused transfer controller, and the fused bypass controller is coupled to the power supply line.

TECHNICAL FIELD

Embodiments of the present disclosure relate to a medium voltage drive system, more particularly, to an arc resistant medium voltage drive system and motor control center for bypass and synch transfer.

BACKGROUND

Medium voltage drive systems are often used to power heavy machinery, such as multiple high horsepower (e.g., 6000 hp) induction motors. FIG. 1 illustrates an example system having two such motors 101 a,b. Each motor 101 a,b may be driven by electrical current supplied from a power supply line 102, and through corresponding fused medium voltage bypass controllers 103 a,b. The bypass controllers 103 a,b may include a switch, a fuse that may be rated to carry large amounts of current, a contactor, and a current sensor.

The individual bypass controllers 103 a,b may connect the motors 101 a,b to the supply line 102 to allow the motors 101 a,b to be run “across the line,” or directly using the currents and phases of the supply line 102. However, during a startup procedure, it may be desirable to control one of the motors at less than normal frequency and thus operate the motor at some reduced speed because of load (e.g. pump) requirements.

Accordingly, during startup, the bypass controllers 103 a,b are taken out of the control lines for the motors 101 a,b. Instead, a variable frequency drive 104 may be connected, via a non-fused medium voltage transfer controller 105 a, to the idle motor 101 a. The variable frequency drive 104 may gradually vary the voltage and frequency supplied to the motor 101 a through the non-fused transfer controller 105 a, to gradually bring motor 101 a up to speed.

Depending on load requirements, the individual motors 101 a,b may be brought up to speed sequentially, so that a first motor 101 a is brought up to speed before a second one 101 b. In such a case, the transfer controllers 105 a,b are also sequentially added to the control lines (e.g., controller 105 a is used during startup of motor 101 a, controller 105 b is used during startup of motor 101 b, etc.).

The commercially-available bypass controllers 103 a,b that are rated for large levels of current (e.g., greater than 400 amps) are only offered for sale in single, standalone cabinets, as depicted in FIG. 1. The individual cabinets house just the components needed for the controller 103 a,b, and do not offer additional space for additional controllers. As a result, significant amounts of floor space are required to support the various individual cabinets shown in FIG. 1. Even more space is occupied with the cabling, such as supply line 102, output bus 106, and lines 107 a,b.

During a normal operation state, the cabinets containing each of the described components may protect the surrounding environment from a produced arc by being constructed to adhere to an arc resistant standard. While in the bypass and/or synchronization processes, an arc fault may be capable of occurring due to high current when both requisite contactors are closed. Because the cabinets are constructed or designed to be arc resistant, the arc fault would not affect structures external to the cabinets, but it is costly to construct and retro-fit the cabinets with thicker material to satisfy the arc resistant standards.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and its features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a configuration of a medium voltage variable frequency drive control system having a single bus system, in accordance with an embodiment of the present disclosure;

FIG. 2A illustrates a medium voltage variable frequency drive control system having a 2-high controller configuration with a dual bus system, in accordance with an embodiment of the present disclosure;

FIG. 2B illustrates an alternative configuration for the medium voltage variable frequency drive control system of FIG. 2A, in accordance with an embodiment of the present disclosure;

FIG. 3 illustrates the electrical components of the 2-high controller configuration of the medium voltage variable frequency drive control system of FIGS. 2A-B, in accordance with an embodiment of the present disclosure;

FIG. 4 illustrates a computer or server that may be used with the medium voltage drive control system, in accordance with an embodiment of the present disclosure;

FIG. 5 illustrates a method of using a 2-high controller configuration of the medium voltage variable frequency drive control system of FIGS. 2A-3, in accordance with an embodiment of the present disclosure;

FIG. 6 illustrates an isometric view of the medium voltage output/bypass system, in accordance with an embodiment of the present disclosure;

FIG. 7 illustrates a front view of the medium voltage output/bypass system, in accordance with an embodiment of the present disclosure;

FIG. 8 illustrates a back view of the medium voltage output/bypass system, in accordance with an embodiment of the present disclosure;

FIG. 9 illustrates a side, cross-sectional view of the medium voltage output/bypass system, in accordance with an embodiment of the present disclosure;

FIG. 10A illustrates the system of FIG. 3 in designated arc energy zones, in accordance with an embodiment of the present disclosure;

FIG. 10B illustrates the system of FIG. 3 further utilizing a reactor compartment in designated zones, in accordance with an embodiment of the present disclosure; and

FIG. 11 illustrates a circuit schematic of the system of FIG. 10B, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

Illustrative embodiments of the present disclosure are described in detail herein. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation specific decisions must be made to achieve developers' specific goals, such as compliance with system related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of the present disclosure. Furthermore, in no way should the following examples be read to limit, or define, the scope of the disclosure.

FIG. 2A illustrates an exemplary embodiment of a 2-high controller configuration for a medium voltage variable frequency drive control system 200. Medium voltage drive control systems 200 may be in the range of about 2300 to about 7200 Volts. The drive control system 200 may include a motor control cabinet 201 a,b for each motor 101 a,b being controlled. In embodiments, any suitable horsepower drives may be used. The cabinet 201 a,b may include portions stacked one above the other. A first portion 202 may include the bypass controller 103 components (referring to FIG. 1), and a second portion 203 may include the transfer controller 105 components (referring to FIG. 1). Stacking the components in this manner may help conserve floor space and stacking the high-heat generating portion (the bypass controller 103 and its fuse) at the bottom helps reduce the risk of that portion receiving extraneous heat generated by other portions, such as the transfer portion 203.

The top-most portion of the cabinet may include an output bus portion 204. The output bus portion 204 may include an extendable output bus 106 (referring to FIG. 1), wiring harnesses, and trays to carry the output bus cabling from the transfer controller 105 to the variable frequency drive 104. In some embodiments, the output bus wiring from neighboring cabinets 201 a,b may be routed across the tops of those cabinets in the output bus portions 204, and to a cabling transition cabinet, such as an end output bus cabinet 205. The end output bus cabinet 205 may be a vertical cabinet having an aperture (not shown) at the top to receive output bus wiring from the motor control cabinets 201 a,b, wiring harnesses, and trays to carry the output bus wiring outside of the end output bus cabinet 205, where they may run over to the cabinet housing the variable frequency drive 104. FIG. 2A illustrates this output bus wiring as laying on the floor, but the output bus wiring may be routed in another wiring tray if desired between the output bus cabinet 205 and the cabinet housing the variable frequency drive 104.

The system 200 may also include a second cabling transition cabinet, in the form of a supply line cabinet 206, which may receive the supply line 102, and which may route that supply line to the neighboring motor control cabinets 201 a,b. The supply line 102 may be routed into each of the bypass portions 202 of the motor control cabinets 201 a,b, forming an extendable supply bus 107. If desired, the bypass portion 202 may further include a power supply line portion, which may have its own wiring harnesses and trays to carry the supply line 102 to the respective bypass controllers 103 a,b (referring to FIG. 1). The system 200 may further include cabling connecting the variable frequency drive 104 to the supply line 102. The cabling connecting the variable frequency drive 104 to the supply line 102 may be external and/or internal to the cabinet housing the variable frequency drive 104.

To further consolidate the components, a modified system 250 is shown in FIG. 2B having the cabinet housing the variable frequency drive 104 attached to one end of the components shown in FIG. 2A (with output bus cabinet 205 moved to the right-hand side for ease of illustration, and omitting the supply line cabinet 206 as shown in FIG. 2A). Indeed, the motor control cabinets 201 a,b, the cabling transition cabinets 205, 206, and the cabinet housing the variable frequency drive 104 may be arranged in any suitable manner and/or order. For example, all of the cabinets may be arranged side by side and abut each other. Alternatively, the cabinets may be spaced apart. The modified system 250 may further include at least one cabling transition cabinet configured to house cabling between controllers. With the output bus 106 and supply line bus 107 being extendable, additional motor control cabinets 201 may be added to the modified system 250 in a modular and compact manner.

FIG. 3 illustrates the basic electrical components of the drive control system 200, with cabinet housings illustrated in dashed lines. As shown in FIG. 3, the motor control cabinets 201 a,b may each include a top portion 303 that corresponds to the transfer portion 203 (e.g., FIG. 2A), and a bottom portion 302 that corresponds to the bypass portion 202 (e.g., FIG. 2A). A first fused bypass controller 103 a may be housed within the bottom portion 302 and a first non-fused (e.g., omitting a fuse in the primary control line) transfer controller 105 a within the top portion 303 of the first motor control cabinet 201 a. The second motor control cabinet 201 b may include a second fused bypass controller 103 b housed within the bottom portion 302 and a second non fused transfer controller 105 b within the top portion 303. The extendable supply bus 107 may extend through the bottom portion 302 of the motor control cabinets 201 a,b and provide power to each of the bypass controllers 103 a,b.

As illustrated, the extendable output bus 106 may extend through the top portion 303 of the motor control cabinets 201 a,b and electrically couple each of the transfer controllers 105 a,b to the variable frequency drive 104. The extendable output bus 106 may be housed within a top bus cabinet 304 that is positioned above or on top of the motor control cabinets 201 a,b. In this embodiment, the extendable supply bus 106 extends downward through the top of the motor control cabinets 201 a,b to couple the transfer controllers 105 a,b to the variable frequency drive 104. Alternatively, the top bus cabinet 304 may simply be an internal portion of the motor control cabinet 201 a,b.

The bypass controllers 103 a,b may include any necessary components for directing power from the supply line 102 to the motors 101 a,b, while bypassing the variable frequency drive 104, to run the motors across the line. For example, each of the bypass controllers 103 a,b may include a switch 305 a,b, a fuse 306 a,b, a contactor 307 a,b, and a protection sensor 308 a,b (for example, a current sensor). The transfer controllers 105 a,b may include any necessary components for transferring power to the motors 101 a,b between the power supply line 102 and the variable frequency drive 104. For example, each of the transfer controllers 105 a,b may include a switch 309 a,b and a contactor 310 a,b, but may omit a fuse rated for high currents (for example, greater than 400 Amps). In embodiments, the contactors 307 a,b may be configured to connect the supply line 102 to the motor 101 a,b for a bypass operation. In embodiments, the contactors 310 a,b may be configured to connect a drive output to the motor 101 a,b for variable speed operation. In embodiments, the switches 305 a,b and/or switches 309 a,b may be configured to isolate a circuit from the source of power (for example, supply line 102). The components of the bypass controllers 103 a,b and transfer controllers 105 a,b may all be rated to carry large amounts of current, greater than 400 Amps, and voltages between 2300 and 7200 volts, which are used in medium voltage systems 200.

Due to the heat-sensitivity of a fused-controller and the heat generated by the fuses in the bypass controllers 103 a,b, only one fused controller can be located within a single cabinet in the prior art system shown in FIG. 1. However, by placing a less heat-sensitive controller, e.g., a non fused controller, within the same cabinet, the required cabinetry and floor space required for a drive control system 200 may be decreased. The non-fused transfer controllers may be positioned above the fused bypass controllers to reduce the number of required cabinets without subjecting the fused bypass controllers to additional heat.

In embodiments, the variable frequency drive 104 may include any necessary components to bring the motors 101 a,b up to speed and stop the motors 101 a,b. For example, as illustrated in FIG. 3, the variable frequency drive 104 may include inductors 311, a transistor inverter 312, a rectifier 313, a transformer 314, contactors 315, fuses 316, and a switch 317. In embodiments, the rectifier 313 may be configured to convert alternating current to direct current. In embodiments, the transformer 314 may be configured to transform the voltage of the supply line 102 into multiple isolated lower secondary voltages to power the rectifier 313. In embodiments, the fuses 316 may be configured to interrupt current when the current reaches a limiting range and prohibit the current from reaching its maximum prospective instantaneous value. The variable frequency drive 104 may include additional components or alternative arrangements of components, other than the arrangement illustrated in FIG. 3, within the scope of the invention.

The system 200 may further include software and/or hardware on a computing platform, such as a network server or computer, to control the operation of the various components of the system 200. For example, a controller/computer may control the operation of the various contactors (307, 310) to couple and decouple the bypass and transfer controllers from the supply line 102 and variable frequency drive 104. FIG. 4 illustrates the general hardware elements of such a server or computer 400. The server or computer 400 may include one or more processors 401, which may execute instructions of a computer program to perform any of the features described herein. Those instructions may be stored in any type of computer readable media or memory 402, to configure the operation of the processor 401. For example, instructions may be stored in a read only memory (ROM), random access memory (RAM), removable media, such as a Universal Serial Bus (USB) drive, compact disk (CD) or digital versatile disk (DVD), floppy disk drive, or any other desired electronic storage medium. Instructions may also be stored in a hard drive 403. The server or computer 400 may include one or more output devices, such as a monitor 404, speakers, or printers. The output devices may be controlled by one or more output device controllers 405, such as a video processor. There may also be one or more user input devices, such as a keyboard 406, mouse, touch screen, microphone, etc., which may be connected to the processor 401 through a user interface 407. The server or computer 400 may also include one or more network interface 408, such as a modem or network card to communicate with network 409. The network interface 408 may be a wired interface, wireless interface, or a combination of the two.

In operation, the system 200 of FIG. 2A may be used to power different types of machinery, such as pumping systems. To power a pumping system, each motor 101 a,b may power a separate pump 207 a,b, respectively, as shown in FIG. 2A. With reference now to FIG. 5, FIG. 5 illustrates a method 500 of using the drive control system 200 to start and operate the motors 101 a,b for pumps 207 a,b. Although the illustrated example only shows two motors 101 a,b and pumps 207 a,b, any desired number of motors and pumps may be used. As shown, system 200 includes one motor 101 a,b for each motor control cabinet 201 a,b. Alternatively, additional motors may be connected in parallel with one of the motors 101 a,b, such that the motors are controlled by one motor control cabinet 201 a,b and operate as a single motor.

In step 501, value n may be set to 1 (n will be used to step through the various motors in the system). In step 502, the non-fused transfer controller corresponding to the nth motor may be added to the control line circuit, while the corresponding bypass controller may be removed from the circuit. Using FIG. 3 for example, for starting the first motor 101 a, switch 309 a may be closed to add the transfer controller 105 a to the circuit for motor 101 a, while switch 305 a may be opened to remove the bypass controller 103 a from the circuit for motor 101 a. In that switch configuration, the variable frequency drive 104 is connected to the motor 101 a through the transfer controller 105 a.

Then, in step 503, variable frequency drive 104 may begin to apply electrical pulses to the motor being started. Those pulses may be set at an initial frequency. In step 504, the system may determine whether the motor has reached a predetermined operating speed. This determination may be made using any desired measuring technique (e.g., monitoring the rotational speed of a motor rotor), and using any desired value (e.g., stored in system memory) as the predetermined operating speed. If, in step 504, the motor has not reached the predetermined operating speed, then the system may proceed to step 505, in which the variable frequency drive 104 may increase or decrease the frequency of its pulses, and the process may return to step 503 to apply the modified frequency pulses to the motor. This loop may continue as long as desired or until the motor reaches maximum operating speed. In this manner, the speed of the motor may be regulated.

If the motor has reached its maximum operating speed, the system may then set the switches in step 506 (or contactors—in some embodiments, the switches are manually operated and used for safety purposes, the “switching” herein may be performed using computer-controlled contactors) to run the motor across the line. In FIG. 3 for example, for the first motor 101 a, this may involve opening contactor 310 a in transfer controller 105 a to remove the variable frequency drive 104 from the line of motor 101 a, and to close the contactor 307 a to connect bypass controller 103 a to the line of motor 101 a (thereby “bypassing” the variable frequency drive 104 in the motor's control line). In that configuration, motor 101 a is connected to the bypass controller 103 a, which in turn is directly connected to the supply line 102, and the current from the supply line 102 may be used to directly run motor 101 a. This transfer of control may include synchronizing the frequencies of the variable frequency drive 104 with that on the supply line 102.

When the Nth motor is running across the line, the system 200 may then proceed to step 507 to determine if another motor should be started. The determination to start another motor may be based on a level of need (if another motor is needed), or a user command entered into the system (e.g., via a computer as shown in FIG. 4). To start the next motor, the system 200 may proceed to step 508, increasing N (to signify the next motor), and resetting the variable frequency drive 104 to the initial motor start frequency. The system may then return to step 502, and the variable frequency drive 104 may once again begin to apply current to start the next motor (for example, motor 101 b). If, in step 507, no more motors are needed, then the method 500 may conclude. Alternatively, the method 500 may await in step 507 until another motor is needed.

The discussion above illustrates starting up motors, but a similar process may be used when it is necessary to stop or adjust the speed of a running motor. There, the transfer controller for the corresponding motor may be connected to the motor, with the variable frequency drive 104 synchronized to the current operating speed of the motor, and the motor's bypass controller may be removed from the circuit (by setting the switches as needed, such as in step 502). Then, the variable frequency drive 104 may apply gradually different (for example, stepping down or up) frequency pulses to adjust the motor speed as needed. The transfer may occur by opening contactor 307 b in the second bypass controller 103 b and closing contactor 310 b in the second transfer controller 105 b. The variable frequency drive 104 may then adjust the speed of the second motor 101 b, by adjusting the electrical pulses sent to the second motor 101 b, until the second motor 101 b stops (or reaches the desired new speed).

In the system 200, operation is facilitated by processor 401 or an equivalent automated device sending signals to actuators that are configured to open and close the contactors. While only two motors are shown in FIG. 3, any number of motors may be started and transferred to run off of the supply line 102.

Referring now to FIG. 6, FIG. 6 illustrates an exemplary embodiment of one of the motor control cabinets 201 a,b. As illustrated the bypass portion 202 may comprise a first door 600, and the transfer portion 203 may comprise a second door 601. The first door 600 may be configured to contain and/or provide access to the internal components disposed within the bypass portion 202. The second door 601 may be configured to contain and/or provide access to the internal component disposed within the transfer portion 203. Both the first door 600 and the second door 601 may be any suitable size, height, shape, and combinations thereof. In some embodiments, the first door 600 may have equivalent dimension to the second door 601. In other embodiments, the first door 600 may have different dimensions from the second door 601. Without limitations, the first door 600 and/or the second door 601 may have a suitable thickness, such as from about 0.05 to about 0.20 inches. In embodiments, the first door 600 and/or the second door 601 may have a thickness of about 0.12 inches. In embodiments, the first door 600 and/or the second door 601 may be arc resistant, wherein being arc resistant is defined as meeting a defined standard so as to protect against an arc.

In embodiments, the Institute of Electrical and Electronics Engineers (IEEE) standard C37.20.7 provides for testing guidelines for confirming arc resistant capability of metal-enclosed switchgear (i.e., motor control cabinets 201 a,b). The standard provides for different ratings designated as types, wherein a first type is only arc resistant at the front and wherein a second type is fully arc resistant. Being arc resistant may be defined as having no indications of burns, the doors do not open, no projectiles greater than a certain mass are expelled from the switchgear lower than 2 meters, no holes are burned through the switchgear lower than 2 meters, and all grounds remain intact while an arc occurs for about 0.5 seconds. During operations, an arc may be produced at a variety of points within the motor control cabinets 201 a,b. Without limitations, the arc may occur at line disconnect locations. Undesired or unintended electric arcing may have detrimental effects on electric power transmission, distribution systems, and electronic equipment. Devices which may cause arcing include, without limitation, switches, circuit breakers, relay contacts, fuses, and poor cable terminations. When an inductive circuit is switched off, the current cannot instantaneously jump to zero; a transient arc will be formed across the separating contacts. If a circuit has enough current and voltage to sustain an arc formed outside of a switching device, the arc may cause damage to equipment such as melting of conductors, destruction of insulation, fire, and combinations thereof. For example, an arc flash may be an explosive electrical event that presents a hazard to people and equipment.

As such, the motor control cabinets 201 a,b may be improved by being arc resistant to improve upon safety measures. To improve upon the switchgear to meet the arc resistant standard, the following may be installed: additional bracing to resist high internal pressure, pressure relief flaps that are actuable to open to relieve internal pressure, ventilation that is actuable to close to seal gases produced during an arc, cooling fans to direct any produced gases. In one or more embodiments, the motor control cabinets 201 a,b may further be equipped with double-layer outer wall and/or doors to resist burn-through from the high temperatures produced during an arc. While all of the aforementioned can satisfy the arc resistant standard, they are costly to implement, so improvements to the motor control cabinets 201 a,b to reduce arc energy are beneficial.

Without limitations, the first door 600 and/or the second door 601 may comprise material that is designated as arc resistant, such as 11 GA steel, 10 GA steel, 9 GA steel, 8 GA steel, or any higher gauged steel. In other embodiments, any variety of steel may be used such as stainless, carbonized, galvanized, and the like. As illustrated, both the first door 600 and the second door 601 may comprise a handle 603. The handle 603 may be configured to be gripped and/or rotated to provide movement to the respective door. In embodiments, the first door 600 and/or the second door 601 may rotate along a vertical axis disposed about an opposite side of the door from the handle 603. The first door 600 and/or the second door 601 may further comprise an isolation handle 606 disposed about a side edge 605 of the first door 600 and the second door 601. Without limitations, each isolation handle 606 may be configured to be actuated so as to engage with an interior component within the motor control cabinet 201 a,b. In embodiments, the isolation handle 606 corresponding to the first door 600 may be coupled to the switch 305 a,b (referring to FIG. 3). During operation, actuation of this isolation handle 606 may connect or disconnect the switch 305 a,b. In embodiments, the isolation handle 606 corresponding to the second door 601 may be coupled to the switch 309 a,b (referring to FIG. 3). During operation, actuation of this isolation handle 606 may connect or disconnect the switch 309 a,b

The first door 600 may further comprise an air vent 607. The air vent 607 may allow fluid communication (for example, air) from the external environment into one of the motor control cabinets 201 a,b. In embodiments, the air vent 607 may be implemented to contribute to the arc resistance of the motor control cabinets 201 a,b. Air may be provided to the internal components of one of the motor control cabinets 201 a,b as necessary. For example, air vent 607 may allow air to flow into one of the motor control cabinets 201 a,b for convection cooling of any internal components experiencing high temperatures. In the event of an arc occurring within one of the motor control cabinets 201 a,b, the air vent 607 may be actuated to close, thereby protecting the surroundings from the effects of an arc.

At least one of the motor control cabinets 201 a,b may further comprise a plenum 608 disposed atop the motor control cabinet 201 a,b. In embodiments, exhaust produced from an arc may be collected within the plenum 608. As illustrated, the plenum 608 may be coupled to a plenum exhaust 609. In embodiments, the plenum exhaust 609 may vent any potential arc exhaust collected within the plenum 608 out of and away from the motor control cabinet 201 a,b and the surroundings.

FIGS. 7-9 illustrate other embodiments of one of the motor control cabinets 201 a,b. FIG. 7 illustrates a front view of one of the motor control cabinets 201 a,b. FIG. 8 illustrates a back view of one of the motor control cabinets 201 a,b. FIG. 9 illustrates a side, cross-sectional view of one of the motor control cabinets 201 a,b. As illustrated in FIG. 7, the first door 600 may comprise a motor connection 700. In embodiments, the motor connection 700 may be any suitable port or connector used to connect the motor control cabinet 201 a,b to the motors 101 a,b (referring to FIG. 1). In embodiments, the entirety of the motor control cabinets 201 a,b may be designed to be arc resistant. As illustrated, the motor control cabinet 201 a,b may comprise a first rear cover 800 and a second rear cover 801. The first rear cover 800 and/or the second rear cover 801 may provide protection from effects caused by an arc. Both the first rear cover 800 and the second rear cover 801 may be any suitable size, height, shape, and combinations thereof. In some embodiments, the first rear cover 800 may have equivalent dimension to the second rear cover 801. In other embodiments, the first rear cover 800 may have different dimensions from the second rear cover 801. Without limitations, the first rear cover 800 and/or the second rear cover 801 may have a suitable thickness, such as from about 0.05 to about 0.15 inches. In embodiments, the first rear cover 800 and/or the second rear cover 801 may have a thickness of about 0.12 inches. Without limitations, the first rear cover 800 and/or the second rear cover 801 may comprise material designated as arc resistant, such as 11 GA steel, or any of the other materials described for the first door 600 and the second door 601. As illustrated, the second rear cover 801 may be disposed above the first rear cover 800 in relation to a vertical axis of the motor control cabinet 201 a,b. In embodiments, the first rear cover 800 may be disposed about the bypass portion 202 (referring to FIG. 2A) of the motor control cabinet 201 a,b, and the second rear cover 801 may be disposed about the transfer portion 203 of the motor control cabinet 201 a,b. Both the first rear cover 800 and the second rear cover 801 may be removable coupled to the motor control cabinet 201 a,b. Without limitations, the first rear cover 800 and the second rear cover 801 may be fastened to the motor control cabinet 201 a,b using any suitable fasteners such as bolts. Both the first rear cover 800 and the second rear cover 801 may provide access to the rear of the motor control cabinet 201 a,b.

The motor control cabinet 201 a,b may further comprise a low voltage compartment 803. As illustrated, the low voltage compartment is disposed within the bypass portion 202 and in between the first door 600 and the second door 601. In one or more embodiments, the low voltage compartment 803 may comprise monitoring equipment, control equipment, terminal blocks, connections to external controls, relays, and combinations thereof. In further embodiments, the low voltage compartment 803 may be rated as arc resistant.

With regards to the present disclosure, FIGS. 10A, 10B, and 11 illustrate embodiments of the configuration of the system 200 before and after implementing a reactor compartment 1000. FIG. 10A illustrates the system 200 as shown and described by FIG. 3. FIG. 10B illustrates the system 200 incorporated with the reactor compartment 1000. FIG. 11 illustrates a circuit schematic of FIG. 10B. In embodiments, the current output from the transfer controllers 105 a,b (as shown on FIG. 11) and/or bypass controllers 103 a,b (as shown on FIG. 11), may be greater than the operating capacity of the inverter (as shown on FIG. 11) as the current switches between the variable frequency drive 104 and the motor control cabinet 201 a,b. Such an arrangement may allow an arc fault that would occur in the output of the inverter 312 to be exposed to a large current load during synchronization transfer and/or bypass when both contactors 307 a, 310 a or 307 b, 310 b are closed. FIG. 10A provides for the system 200 to operate to remain arc resistant by reinforcing the inverter compartment. FIGS. 10B and 11 illustrate the system 200 comprising the reactor compartment 1000 to reduce the current potential available to a compartment containing inverter 312 (for example, inverter compartment 1105 on FIG. 11) thereby increasing an inherent safety factor of the system 200.

As illustrated in FIGS. 10A-10B, the system 200 may be subjugated to certain “zones” of energy potential that could result in producing an arc. Zone 1 refers to a designation of equipment within the system 200 where there is the highest energy potential for a resultant arc. Zone 2 refers to a designation of equipment within the system 200 where there is a high energy potential for a resultant arc. Zone 3 refers to a designation of equipment within the system 200 where there is the lowest energy potential for a resultant arc. As shown in FIG. 10A, motor control cabinets 201 a,b and the cabinet housing at least a portion of the variable frequency drive 104 are within Zone 1 while the remaining portion of the variable frequency drive 104 is in Zone 2. In the disclosed embodiment of FIG. 10A, each cabinet and/or compartment housing a component of the system 200 may be designed to be arc resistant. This may prohibit any potential arc from affecting the external environment from the cabinets and/or compartments as there is a high energy potential of an arc occurring. As shown in FIG. 10B, the motor control cabinets 201 a,b and the cabinet housing at least a portion of the variable frequency drive 104 are within Zone 1. In this embodiment, the compartment housing the transformer 314 and/or rectifier 313 (referring to FIG. 3) of the variable frequency drive 104 is in Zone 2, and the compartment housing the inverter 312 of the variable frequency drive 104 is in Zone 3 because the system 200 further comprises the reactor compartment 1000. In this embodiment, the reactor compartment 1000 is in Zone 2 as well. In the disclosed embodiment of FIG. 10B, each of the motor control cabinets 201 a,b, reactor compartment 1000, and the cabinets and/or compartments housing a portion of the variable frequency drive 104 may be designed to be arc resistant. As the system 200 is using the reactor compartment 1000, the current available to the compartment containing inverter 312 (for example, inverter compartment 1105 on FIG. 11) may be reduced by a determined percentage. This may reduce the energy of an arc being produced during bypass or synchronization. Without limitations, one skilled in the art may be able to arrange the individual compartments and/or cabinets housing the components of the system 200 in any suitable fashion as long as the electrical configuration of the system 200 is properly operational.

With reference now to FIG. 11, the reactor compartment 1000 may be disposed between the motor control cabinets 201 a,b and cabinet housing the variable frequency drive 104. In embodiments, the reactor compartment 1000 may be a compartment of a cabinet or may be a separate cabinet itself. In one or more embodiments, the reactor compartment 1000 may be constructed of, designed with, or comprised of material designated as arc resistant. In embodiments, the reactor compartment 1000 may be configured to house a reactor 1100 disposed therein.

In embodiments, the reactor 1100 may be electrically coupled between the output of the inverter 312 and the transfer controllers 105 a,b which are also connected to the power source through the bypass controllers 103 a,b during a bypass or synchronization operation when both contactors are closed. The reactor 1100 may be configured to provide additional inductance to the circuit. In embodiments, any suitable electro-magnetic device may be used for the reactor 1100, such as, but not limited to a 3-phase line or load reactor. Without limitations, the reactor 1100 may be able to maintain a saturated inductance of over 80% of normal operating inductance, and the current available to the compartment containing inverter 312 (for example, inverter compartment 1105) during bypass or synchronization transfer may be reduced by over 50%. Due to the reduced current load going to the inverter 312, an inverter compartment 1105 containing inverter 312 may not need to be designed to be arc resistant or may be minimally reinforced to withstand the reduced arc energy of Zone 3 rather than the more significant reinforcement required to contain the higher arc energy of Zone 2.

Although the disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the following claims. 

What is claimed is:
 1. A drive control system comprising: a variable frequency drive cabinet comprising a variable frequency drive; a power supply line; at least one motor control cabinet having a top portion and a bottom portion, wherein the at least one motor control cabinet is arc resistant, wherein the at least one motor control cabinet comprises: a medium voltage fused bypass controller in the top portion; a medium voltage non-fused transfer controller in the bottom portion; a reactor compartment, wherein the reactor compartment is arc resistant; wherein the variable frequency drive is coupled to the power supply line and the non-fused transfer controller, and the fused bypass controller is coupled to the power supply line.
 2. The drive control system of claim 1, further comprising: at least one motor, wherein the at least one motor is coupled to the fused bypass controller and the non-fused transfer controller.
 3. The drive control system of claim 1, further comprising: an extendable supply bus in the bottom portion that couples the fused bypass controller to the power supply line; and an extendable output bus in the top portion that couples the non-fused transfer controller to the variable frequency drive.
 4. The drive control system of claim 3, further comprising: at least one cabling transition cabinet housing a portion of cabling between the power supply line and the extended supply bus and housing a portion of the cabling between the extended output bus and the variable frequency drive.
 5. The drive control system of claim 1, wherein the fused bypass controller comprises a switch, a fuse, a contactor, and a protection sensor, and the non-fused transfer controller comprises a switch, a contactor, and a protection sensor.
 6. The drive control system of claim 5, further comprising a processor storing instructions on a computer readable medium, wherein executing the instructions causes the contactor in the non-fused transfer controller to open and the contactor in the fused bypass controller to close, transferring control of the motor from the variable frequency drive to the power supply line.
 7. The drive control system of claim 1, wherein the reactor compartment comprises a reactor.
 8. The drive control system of claim 7, wherein the reactor is configured to provide additional inductance to the circuit, wherein the reactor is electrically coupled between the output of an inverter and the non-fused transfer controller.
 9. The drive control system of claim 8, further comprising an inverter compartment, wherein the inverter is disposed within the inverter compartment, wherein the reactor reduces the current available to the inverter compartment during bypass or synchronization transfer by over 50%.
 10. A drive control system comprising: a first motor control cabinet, wherein the first motor control cabinet is arc resistant, comprising: a first fused medium voltage bypass controller; and a first non-fused medium voltage transfer controller disposed below the first fused medium voltage bypass controller; a second motor control cabinet, wherein the second motor control cabinet is arc resistant, comprising: a second fused medium voltage bypass controller; and a second non-fused medium voltage transfer controller disposed below the second fused medium voltage bypass controller; an extendable supply bus coupled to the first fused medium voltage bypass controller, the second fused medium voltage bypass controller, and a power supply line; an extendable output bus coupled to the first non-fused medium voltage transfer controller and the second non-fused medium voltage transfer controller; a reactor compartment, wherein the reactor compartment is arc resistant; and a variable frequency drive cabinet comprising a variable frequency drive, wherein the variable frequency drive is coupled to the extendable output bus and the power supply line.
 11. The drive control system of claim 10, further comprising: a first motor and a second motor, wherein the first fused bypass controller and the first non-fused transfer controller are coupled to the first motor, and wherein the second fused bypass controller and the second non-fused transfer controller are coupled to the second motor.
 12. The drive control system of claim 11, wherein the variable frequency drive is configured to regulate the speed of the first motor and second motor and to start and stop the first motor and the second motor.
 13. The drive control system of claim 10, further comprising: at least one cabling transition cabinet housing a portion of cabling between the power supply line and the extended supply bus and housing a portion of cabling between the extended output bus and the variable frequency drive.
 14. The drive control system of claim 10, wherein each of the first fused medium voltage bypass controller and the second fused medium voltage bypass controller includes a switch, a fuse, a contactor, and a protection sensor.
 15. The drive control system of claim 10, wherein each of the first non-fused medium voltage transfer controller and the second non-fused medium voltage transfer controller includes a switch, a contactor, and a protection sensor.
 16. The drive control system of claim 10, wherein the extendable output bus is housed within a top cabinet positioned above the first motor control cabinet and the second motor control cabinet, a portion of the extendable supply bus is housed within the first motor control cabinet, and a portion of the extendable supply bus is housed within the second motor control cabinet.
 17. The drive control system of claim 10, wherein the reactor compartment comprises a reactor.
 18. The drive control system of claim 17, wherein the reactor is configured to provide additional inductance to the circuit, wherein the reactor is electrically coupled between the output of an inverter and the first and second non-fused medium voltage transfer controllers.
 19. The drive control system of claim 18, further comprising an inverter compartment, wherein the inverter is disposed within the inverter compartment.
 20. The drive control system of claim 19, wherein the reactor reduces the current available to the inverter compartment during bypass or synchronization transfer by over 50%. 